1. Field to the Invention
The present invention relates to a ball motion measuring apparatus. More particularly, the present invention relates to a ball motion measuring apparatus for measuring various kinds of motions of balls such as a golf ball, a baseball ball, a tennis ball, and the like after hitting.
2. Description of the Related Art
There have been provided apparatuses and methods for measuring various kinds of motions of balls such as a golf ball after hitting, namely, the speed, rotational amount, the angle of elevation, and the deflection angle thereof with respect to a predetermined flight direction.
FIG. 5 shows a method 1 of measuring a golf ball disclosed in Japanese Patent Application Laid-Open No.3-210282. In the measuring method 1, the image of the golf ball immediately after hitting is photographed by a first camera 2 disposed vertically to the golf ball and higher than the golf ball and a second camera 3 disposed horizontally or by only the first camera 2, with a strobe 4 emitting light to the golf ball.
FIG. 6A shows a method 5 of measuring a golf ball disclosed in Japanese Patent Application Laid-Open No.10-186474. In the measuring method 5, the motion of the golf ball after hitting is measured by first and second cameras 7-1 and 7-2 installed in front of a tee 6. The first and second cameras 7-1 and 7-2 photograph images 9-1 and 9-2 of the golf ball at different times by differentiating shutter opening/closing times determined by detection of a sensor 8 installed rearward from the tee 6, as shown in FIG. 6B.
In addition, in a measuring apparatus disclosed in each of Japanese Registered Patent Nos.2879881 and 2950450, two cameras are used to photograph the image of a golf ball immediately after hitting. The motion of the golf ball such as its speed, its rotational amount, and the like is computed by a controlling/computing device, based on the image of the golf ball photographed by the above-described measuring methods or apparatuses.
In the measuring method 1 shown in FIG. 5, the shutter of each camera is always open to photograph the golf ball at predetermined intervals by flashing the strobe 4 two or more times. Thus, it is necessary to reduce the degree of aperture opening of each camera to keep the shutter always open. The amount of light emitted by the strobe is insufficient outdoors because there is too much sunlight outdoors. Thus, it is difficult to obtain an image having a clear contour of the ball. Therefore, to compensate for clearness of the golf ball in analyzing the motion of the golf ball, it is necessary to put a required mark on the golf ball surface to be photographed. It is also necessary to locate the first camera 2 at a position immediately above the golf ball. Thus, much time and labor are required in preparation for measurement.
The camera 7-1 and 7-2 which are used in the measuring method 5 shown in FIG. 6A captures only one ball image into one image frame. Moreover, because the opening/closing speed of the shutter is not high enough to capture a plurality of images of the ball at a very high speed, a plurality of cameras are required to capture a plurality of ball images into the image frame at short intervals. Thus, the measuring method 5 causes the measuring apparatus to be complicated and large-scaled. Normally, the motion of the golf ball is photographed outdoors. Thus, it is important that the measuring apparatus is easy to carry. In this respect, the measuring apparatus is not easy to carry and much time and labor are required in installing each camera at a predetermined position.
The measuring apparatus with two cameras disclosed in Japanese Registered Patent Nos.2879881 and 2950450 respectively is also disadvantageous because they have the same problem as that of the measuring method 5. In addition, they require the use of a golf ball on which a reflective dot pattern has been put to compensate for clearness of the image of the ball. In the Registered Patent No.2879881, there is also disclosed that the apparatus can photograph a ball image by only one camera. But a ball image photographed by one camera is incapable of measuring a deflection angle.
The present invention has been made in view of the above-described problem. Accordingly, it is an object of the present invention to provide a ball motion measuring apparatus capable of photographing a ball image with one CCD camera having a multi-shutter, analyzing various motions of a hit ball with high accuracy, easy to carry, and compact.
To solve the problem, there is provided A ball motion measuring apparatus comprising a CCD camera having a multi-shutter capable of successively opening and closing at a plurality of times at a high speed; a triggering sensor detecting a movement of a ball-hitting means or that of a ball and outputting a trigger signal to set opening/closing times of said multi-shutter; and a controlling/computing device connected to said CCD camera and said triggering sensor and having a storing medium for an image frame and an image display means.
Owing to a plurality of successive openings/closings of said multi-shutter caused by detection of said triggering sensor, said CCD camera photographs a plurality of ball images on a one-image frame, and said image display means displays said ball images in said one-image frame.
The conventional shutter-provided CCD camera can capture only one image into the one-image frame. Thus, it is necessary to prepare a plurality of cameras to photograph a plurality of ball images. According to the present invention, it is possible to photograph a plurality of ball images by using one multi-shutter-provided CCD camera. That is, the multi-shutter can successively open and close at a plurality of times at intervals as short as 1.5 ms to 3.0 ms. Therefore, the CCD camera can capture a plurality of ball images into the one-image frame and the ball images can be displayed on a monitor at same time. Because one CCD camera photographs the ball images, it is possible to make the entire measuring apparatus compact and lightweight. Thus, it is possible to reduce time and labor required to carry the component parts of the measuring apparatus and install the camera at a predetermined position.
The multi-shutter is initially opened and closed in association with a trigger signal of the triggering sensor detecting the passage of the ball and so on. Therefore, it is possible to prevent the shutter opening/closing time from being unsynchronous with the passage of the ball and capture the ball image reliably and automatically. As the triggering sensor, it is possible to use a sensor detecting passage of a ball-hitting means, a reflective-type sensor detecting passage of a hit ball, a sound sensor detecting a hitting sound, and the like. A plurality of ball images captured in the one-image frame are sent to the controlling/computing device connected to the CCD camera. Upon receipt of the ball images, the controlling/computing device computes motions of the ball with high accuracy.
According to the present invention, strobes whose number is equal to or more than the number of opening/closing times of said multi-shutter are connected to said controlling/computing device, and said strobes flash sequentially and synchronously with opening/closing times of said multi-shutter. Because a plurality of strobes flash sequentially and synchronously with opening/closing times of said multi-shutter, a ball can be photographed with only the ball irradiated with flashlight owing to a high speed opening/closing of the multi-shutter. Thus, it is possible to prevent capturing of light emitted from objects such as a background other than an object to be photographed and obtain a ball image having a clear contour. Accordingly, it is possible to photograph a ball image clearly and securely when the ball is photographed outdoors although a large amount of light is present there. To irradiate the ball with a sufficient amount of light, it is possible to provide strobes whose number is twice as large as that of the multi-shutter or more and flash a plurality of strobes simultaneously and synchronously with the opening/closing of the multi-shutter.
Because the ball image is photographed with the ball irradiated with flashlight, the contour of the ball is clear and the surface of the ball is photographed clearly. Thus, indication of a brand put on the surface of the ball can be clearly checked. Further, it is possible to measure motions of the ball such as its rotational amount, speed, angle of elevation, and the like with high accuracy without applying a mark to the surface of the ball to be measured. Needless to say, a mark-applied ball can be used to measure its motion as conventionally done.
According to the present invention, said controlling/computing device is connected to a swinging speed measuring sensor, for measuring a swinging speed of said ball-hitting means, having a projector having two projecting parts each emitting a detection ray and a receptor having two light-receiving parts each detecting said detection rays, and said swinging speed measuring sensor is disposed rearward from a ball-hitting position so that said controlling/computing devices measures an interval between a time when said ball-hitting means intercepts one of said detection rays and a time when said ball-hitting means intercepts the other detection ray. Thereby a swinging speed of ball-hitting means is computed. By the swinging speed measuring sensor detecting the swinging speed of the ball-hitting means, the controlling/computing device can compute the swinging speed of the ball-hitting means in addition to motions of the hit ball. Thus, the ball motion measuring apparatus can be utilized to make a composite analysis having the characteristic of the ball. The interval between the two projecting parts is known. Thus, by measuring the interval between the time when said ball-hitting means intercepts one of said detection rays and the time when said ball-hitting means intercepts the other detection ray, it is easy to determine the passage speed of the ball-hitting means.
The swinging speed measuring sensor serving as said triggering sensor is horizontally located at a position, 20 mm to 40 mm rearward from said ball-hitting position, orthogonal to an imaginary straight line extending in a predetermined progress direction of said ball and outputting said trigger signal when said ball-hitting means intercepts said detection rays. The CCD camera is horizontally located at a position, 100 mm to 300 mm forward from said ball-hitting position, orthogonal to said imaginary straight line to photograph images of said ball immediately after hitting.
By using the swinging speed measuring sensor as the triggering sensor, it is unnecessary to provide the ball motion measuring apparatus with the triggering sensor separately from the swinging speed measuring sensor. Thus, it is possible to simplify the construction of the ball motion measuring apparatus applicable to various measurements, and thus the swinging speed measuring sensor is easy to carry. The analysis of the motion of the ball immediately after hitting is very important in judging the ball performance and the characteristic performance of the ball-hitting means. In this respect, it is necessary that the image of the ball is clear to make correct judgement. Accordingly, by disposing the swinging speed measuring sensor serving as said triggering sensor in the above-described range and disposing the CCD camera at the above-described position, the image of the ball immediately after hitting can be securely captured. Consequently, a correct judgement can be made on the ball performance and the characteristic performance and of the ball-hitting means.
Based on a plurality of images of a ball photographed in said one-image frame, said controlling/computing device determines a central coordinate of each of images of said ball and computes an actual movement distance of said ball and a flight speed of said ball from an interval between an opening/closing time of said multi-shutter and a successive opening/closing time of that. Owing to the pre-calibration of the CCD camera, the controlling/computing device of the present invention can make the movement amount of the ball image in the image frame and the actual movement of the ball relative to each other from the images of the ball captured into the one-image frame. Based on the determined actual movement distance of the golf ball and the shutter opening interval corresponding to the time period required for the ball to travel the actual movement distance, the controlling/computing device determines the flight speed of the ball.
According to the present invention, based on a plurality of images of a ball photographed in said one-image frame, said controlling/computing device computes an angle of a trajectory passing through central coordinates of images of said ball with respect to a horizontal direction pre-calibrated on said one-image frame to compute a flight angle of said ball with respect to an actual horizontal line. Because the horizontal calibration made on the image frame allows the relationship between the trajectory of the ball and the horizontal direction to be easily analyzed. Thus, the angle of elevation can be easily computed.
Further, according to the present invention, said controlling/computing device compares a diameter of each of a plurality of images of a measuring ball in said one-image frame with a diameter of each of reference images of two or more balls pre-photographed by said CCD camera, which stored in said controlling/computing device adding each data of said balls locating at different positions with respect to said imaginary straight line extending in said predetermined progress direction of said balls to determine a distance from said imaginary straight line and compute a deflection angle of said measuring ball with respect to said predetermined progress direction.
The controlling/computing device compares the diameter of the photographed measuring ball images with the diameter of the photographed reference ball images. In this case, owing to positional data of the photographed reference ball image, it is possible to grasp the positional relationship between the photographed measuring ball images and the imaginary straight line. Thus, only one CCD camera allows the deflection angle of the measuring ball to be computed. According to the present invention, the reference ball image is obtained by photographing a ball located at two or more positions of a straight line passing the CCD camera at a right angle with the imaginary straight line. For example, the controlling/computing device stores the data of a ball photographed at a position located at the side of the CCD camera with respect to the imaginary straight line and the data of a ball photographed at a position located at the side opposite to the side of the CCD camera with respect to the imaginary straight line. The controlling/computing device may store data of more reference ball images by photographing a ball at two or more positions.
Further, according to the present invention, based on a plurality of images of a ball photographed in said one-image frame, said controlling/computing device determines a central coordinate of each of a plurality of images of said ball and computes an actual movement distance of a given point on said ball to compute a rotational amount of said ball on a rotational axis passing through a central coordinate of said ball by an interval between an opening/closing time of said multi-shutter and a successive opening/closing time of that. The rotational amount of the ball is important in judging its characteristic and thus essentially measured. In the ball motion measuring apparatus, flashlight is emitted by strobes synchronously with opening/closing time of the shutter. Therefore, the situation of the surface of the ball can be clearly captured and the rotational amount of the ball can be easily computed.
That is, an indication or a pattern showing a brand or the like is put on the surface of the ball. The indication or the pattern can be confirmed on a photographed ball image. Therefore, it is easy to compute the rotational amount of the ball with respect to its rotational axis from a movement situation of the indication or the like on each ball image. According to the ball motion measuring apparatus of the present invention, not only the surface of the ball image but also the contour thereof can be photographed clearly. Thus, it is unnecessary to use a ball on which a particular measuring mark has been put on the golf ball unlike the conventional ball motion measuring apparatus. Thus, much time and labor are not required in preparation for measurement of the motion of the ball, which allows the measurement to be easily accomplished. Needless to say, the ball motion measuring apparatus of the present invention is applicable to measurement of the motion of a golf ball on which a mark has been put, similarly to the conventional measuring apparatus.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.